Rotary kiln control arrangement



Sept. 7, 1937. SMITH ROTARY kn. CONTROL ARRANGEMENT Filed Dec. 12, 1934Wm m s wo i3 3% u s Amfi Patented Sept. 7, 1937 PATENT OFFICE ROTARYKILN conraor. ARRANGEMENT Aubrey Smith, Schenectady, N. Y., assignor toGeneral Electric Company, a corporation of New York Application December12, 1934, Serial No. 757,168

3 Claims.

The present invention relates to rotary kiln control arrangements, morespecifically to the kind of control arrangements used for controllingrotary kilns in cement manufacturing plants, al-

though it is not limited thereto necessarily.

In the present day cement manufacturing plants, inclined rotary kilns ofconsiderable length are provided to effect incipient vitrification orfusion of two materials, one material rich in lime, such as limestone ormarl, known as calcareous material, and another material rich in silica,alumina and iron oxide, such as clay or shale, known as argillaceousmaterial. A homogeneous mixture of these two materials is fed into thehigh end of a rotary kiln and during rotation of the latter passesthrough the different zones thereof, known as dehydration zone,calcining zone, and clinkering zone. At the end of the last zone, thecement clinker is discharged and cooled. The union of the materialswithin the kiln is effected by the. application of heat which in theusual arrangement is produced by a burner projecting into the lower endof the kiln and discharging combustible material therein. The finaltemperature at which incipient fusion or union takes place is of theorder of 1500 centigrade. It is desirable to maintain substantiallyconstant temperature within the kiln because a considerable variation ofthe temperature lowers the quality of the produced cement clinker andalso the efficiency of the kiln.

The object of my invention is to provide an improved construction andarrangement of rotary kiln appurtenances especially an improved controlmechanism for such equipments whereby the quality of the clinker isimproved and the output and thermal efllciency of the kiln increased.

For a consideration of what I believe to be novel and my invention,attention is directed to the following description and the claimsappended thereto in connection with the accompanying drawing.

The single figure of the drawing shows dia grammatically a kiln controlarrangement in accordance with my invention, particularly adapted forthe manufacture of cement.

The arrangement comprises an inclined rotary kiln II) which has a sheetsteel cylinder II, lined inside with refractory brick, or like heatresistant material l2. The cylinder H is rotatably supported on suitablebearings l3 and driven by a motor l5 through a gearing I6. Fuel isconducted into the interior of the lower end of the kiln by a burner I'Ireceiving fuel from a bin l8 through a feed screw l9 driven by a motor20.

(c1. ace-s3) The fuel is forced out of the burner into the kiln byvehicle air which is supplied by a motor compressor 2| having adischarge conduit 22 connected to the burner H. The burner I1 issupported on or near an end plate 23 of the kiln. The end plate 23 issecured to a cylindrical member 24 concentrically surrounding the end ofthe kiln and forming an annular space 25 therewith through whichsecondary air is drawn into the kiln during operation to maintaincombustion. During normal operation an amount of fuel and primary air,depending upon the output of the kiln, is supplied at considerablevelocity through the burner l1, causing a substantially definite amountof air to be drawn into the kiln, which amount of air varies slightly inaccordance with atmospheric conditions. As stated above, the quality ofthe cement or like substance thus produced varies considerably withchanging temperature in the kiln.

In accordance with my invention, I provide an improved regulatingarrangement for the kiln for automatically and manually maintainingsubstantially constant final temperature of the clinker in the kiln.This is accomplished by controlling the speed of the kiln in response tochanges in temperature therein. To this end the motor l5 for driving thekiln is an adjustable speed motor. In the present instance I have shownan A. C. commutator motor with two sets of brushes 26 and 21 which maybe adjusted, that is rotated relatively to each other in eitherdirection by means of a pilot motor 23 connected to the two sets ofbrushes by a gearing 29. The motor l5 and the pilot motor 28 areconnected to lines or conductors 30 and 3|, which latter receive energyfrom a suitable source of A. C. current 32 through a switch 34.The'pilot motor 28 is a reversible motor with one terminal thereofconnected to the line 30 by a conductor or wire 35 and two fields 36 and31 connected to a doublethrow switch 38 for connecting the fields withtwo sets of contacts 39 and 40 respectively. One of the contacts 40 isconnected to the line 3| by a wire 42 including a push-button 43, andthe other contact 40 is connected to the line 3| through a wire 44 and apush-button 45. When the switch 38 is connected with the contacts 40,the pilot motor 28 may be operated manually in either in speed of thevariable speed motor I5, and clos- 1 ing of the other push-button 45causes operation of the pilot motor 28 in the opposite direction,resulting in a decrease in speed of the variable speed motor |5.

During operation, the speed of the kiln is increased in response toincreasing temperature in the clinkering zone, and vice versa, the speedof the kiln is decreased in case the temperature in the clinkering zonedecreases. With this arrangement, substantially constant final maximumtemperature of the clinkered material is maintained, thereby producinghigher quality clinker at improved thermal efiiciency of the kiln.

In accordance with my invention, I provide means for automaticallycontrolling the speed of the kiln in response to temperature changestherein. These means efiect automatic operation of the pilot motor 28whenever the doublethrow switch 38 connected to the fields 36 and 31 ofthe pilot motor engages the contacts 39, as indicated in the drawing.

The means for automatically operating the pilot motor 28 in response totemperature changes in the kiln comprises a temperature responsivedevice,'preferably a photoelectric cell 46, an amplifier 41, and a timedelay relay or contact making and breaking device 48. The provision of atime delay relay is of particular significance in my arrangement in thatit permits operation of the motor 28 for a predetermined time only.Thereafter the operation of the pilot motor 28 is interrupted foranother predetermined time. Thus, from another view J-" point, the timedelay relay or contact making and breaking device 48 causes intermittentoperation of the pilot motor 28, thereby preventing over-travel of thekiln speed changing devices and consequent hunting of various elementsof the operating mechanism. The photoelectric cell is connected to theamplifier 41 by wires 49 and 50 including a resistor 5| and amilliammeter 52. The amplifier 41 is connected to the lines 38 and 3|through reactors 53 grounded by capacitors 54. Various kinds ofamplifiers may be used. The amplifier, in the present instance includesa rectifier and a wave smoothing filter a for supplying a substantiallyconstant D. C. voltage to voltage dividers b and 0, respectively.

'The latter are connected in known manner to a thermionic vacuum valve dhaving a grid e connected through a wire 58 to the photoelectric cell 46whereby the grid potential varies in accordance with temperature changesin the kiln. The voltage dividers b are connected through common gridresistors f to the grids g and h of two discharge valves or tubes 55 and56, respectively, whereby the latter are controlled in response totemperature changes in the kiln. The arrangement is such that duringnormal conditions one of the discharge valves 55 or 56, in the presentinstance the valve 55, is non-conducting and the valve 56 is conducting.Further details of the present amplifier are not described because theydo not form a part of my invention.

An electromagnetic relay 5'! has an operating coil 58 connected to theanode of the discharge tube 55 and another relay 59 has an operatingcoil 66 connected to the-discharge tube 56. The two relays 51 and 59have contact making members 6| and 62 respectively which serve forcontrolling the circuits of two relays 63 and 64 respectively. The relay63 has an operating coil 65 connected to the line 3| by a wire 66 and tothe line 38 by a wire 61 including two contacts 68 adjacent the contactmaking member 6|. The relay 64 has an operating coil 69 connectedthrough a wire 10 and the aforementioned wire 66 to the line 3| andthrough a pair of contacts 12 adjacent the contact making member 62 tothe wire 61.

As pointed out above, the discharge tube 56 is normally conducting.Therefore, the operating coil 68 of the relay 59 is normally energizedand the contacts 12 of the circuit for the relay 64 are normally closedby the contact making member 62. The relay 63 has a contact makingmember I3 for closing a pair of contacts 14 in the circuit of the fieldwinding 31 of the pilot motor 28 and the relay 64 has a contact makingmember 15 for bridging contacts I6 in the circuit of field winding 36 ofthe pilot motor 28. In addition, the relay 63 has another contact makingmember 11 for closing a pair of contacts 18 in the circuit of the timedelay relay 48, and the relay 64 has also another contact making member19 for closing a pair of contacts 89 in the circuit of the time delayrelay 48. The arrangement is such that with the coil 69 of the relay 64energized, the contacts controlled by said relay are opened and with thecoil 65 of the relay 63 deenergized the contacts controlled by thisrelay are also opened, as shown in the drawing.

The time delay relay 48 forms the subject matter of an application ofGoff, Serial No. 748,839, filed October 18, 1934, and therefore isdescribed briefly only. It comprises an intermittently operated relay 8|for intermittently opening and closing a pair of contacts 82, a solenoid83, and a small self-excited synchronous motor 84. The circuit for themotor 84 includes a wire 85 connected to an intermediate point of thesolenoid coil 83 and a wire 85a including a contact making member 86 anda wire 81 connected to an end terminal of the solenoid coil 83. This endterminal of the solenoid coil is connected by a wire 88 to the contacts18 and 80 which in turn are connected by a wire or conductor 89 to theline 30. The other terminal of the solenoid coil 83 is connected by awire 98, a wire 9|, contacts 92, a wire 93, and a wire 94 to the line3|. Thus the solenoid coil 83 is energized when one of the relays 63 or64 is closed. With the time delay relay mechanism in the positionindicated in the drawing, energization of the solenoid coil 83 alsocauses energization of the synchronous motor 84, through the circuitdescribed above, and of a coil 95 for the relay 8|. The coil 95 has oneterminal connected to the wire 9| and another terminal connected througha contact 96, another contact 91, a lever 98, and the aforementionedwire 81 to one terminal of the solenoid coil 83. Energization of thecoil 95 effects closing of the contacts 82 by the relay 8|. This causesenergization of one of the fields of the pilot motor. For instance, withthe contactor 8| and the relay 64 closed, the field coil 36 is connectedto the line 3| through a wire 99, the contacts 16, a wire I89, and thecontacts 82. In case the relay 63 is closed, the pilot motor is operatedin the opposite direction, the field winding 31 then being connected tothe line 3| through a wire |8|, the contacts 14, the wire I00 and thecontacts 82.

As stated above, the relay 8| is automatically energized anddeenergized, that is, it operates intermittently, causing intermittentoperation of the pilot motor 28. Opening and closing of contacts 82 iseffected by the time delay relay whose the desired time delay. Rotationof the timing gear I05 by the gear I06 causes rotation of the pointerI01 and after a predetermined time this pointer I01 unlatches a latchI08 engaging the lever 98. This causes turning movement of the u lever98 by the action of a compressed spring I09 resulting in openingmovement of the contact making member 86, thereby deenergizing thesynchronous motor 04, and simultaneously an opening movement of therelay 8|. The contact 91 of the lever 98 then engages another contact H0and thereby efiects closing of the circuit of another solenoid coil III.One end of the latter coil III is connected through the wire 94 to theline 3|, and the other end is connected through a wire II2, the contactsH0 and 91, the lever 98, the wire 81, the wire 88, and the contacts I8or 80, and the wire 89, to the line 30. Energization of the solenoid IIIcauses a plunger I I3 in cooperative relation with the solenoid coil tobe moved toward the right whereby a bell crank lever H4 similar to thelever I03 is turned and effects engagement between another timing gear II5 and a gear I I6 driven by another small synchronous motor II'I.Thesynchronous motor II'I then is energized, being connected similarlyto the connection of the synchronous motor 84 between a terminal and amid-tap of the solenoid III. Its circuit includes a contact makingmember 8 corresponding to the member 86. The gear II5 when in engagementwith the gear 6 causes rotation of a pointer H9 adjustably secured tothe gear I I5 until the pointer II9 engages a latch I20 and effectsunlatching of a lever I2-I whereby the lever I2I is turned by the actionof a spring I22 and effects opening of the contactor H8, thusinterrupting the circuit for. the synchronous motor In. Turning of thelever I2I also effects opening of the contacts 92 whereby the solenoid83 is dcenergized. Deenergization of the solenoid 83, however, causesresetting of the mechanism. The lever I03 with the gear I05 are movedout of engagement with the gear I06 by gravity. That-is, the gear I05drops and permits relatching between the lever 98 and the lever I08 bythe action of a spring I23 engaging the lower end of the latch I08.

When this occurs, the spring I09 is compressed by the weight of thelever 98. Turning movement of the lever 98 in turn opens the circuit forthe solenoid III, whereby the gear H5 is disengaged from the gear IIG.The lever I2I then drops-by gravity, effecting reengagement with thelatch I20 by action of a spring I24 and also eifecting closing of thecontacts 02 and compression of the spring I22. If by this time one ofthe relays 63 or 64 is still closed, another cycle of operation of thetime delay relay begins similar to the one described above.

The operation of the mechanism as a whole is briefly a's follows.- Theelectronic discharge valve or tube 55, which in substance is a relayenergized in response to temperature changes,. is normallynon-conducting and the tube 56 is normally conducting; hence 'the relay51 is normally open and the relay 59 is normally closed. Both relays 63and 64 are normally open.. A change the temperature of the kiln rises ordrops. operation is continued until normal temperature and a standardamplifying means arrangement is reliable and eifective in operation.

in temperature causes the tube 55 to become conducting or the tube 56 tobecome non-conducting, depending upon whether the temperature increasesor decreases. Such changes effect in one case opening of the relay 62and in the other case closing of the relay 6|, resulting in closing ofone of the relays 63 or64. These relays eifect operation of the timedelay relay or device 48 which intermittently energizes and deenergizesthe coil 95 of the contactor 8|, and thereby effects intermittentclosing and opening of one of the field circuits of the pilot motor 28.Thus, the pilot motor whose circuits in addition'to the contacts 82 alsoinclude one of a pair of contacts 14 or I6 is intermittently operatedand effects an intermittent increase or decrease in speed of thevariable speed motor I5, depending upon whether This in the kiln isreestablished during which conditions the gas filled, grid controlleddischarge valve 55 is non-conducting and the other valve 56 isconducting.

With my invention I have accomplished animproved control mechanism forrotary kilns whereby the speed of these kilns may be automatically andmanually controlled in response to temperature changes of a substanceheated in the kilns. The arrangement is relatively simple. It includes aphotoelectric cell, a standard time delay relay The control Duringoperation, the temperature in the kiln is maintained substantiallyconstant, whereby in many cases, especially where clinker is produced,the products discharged by the kiln are of uniform high quality.

' In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof,but I wish it understood that the apparatus shown and described is onlyillustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The combination of a rotary kiln for heating a substance, a variablespeed motor for driving the kiln, means for conducting fuel and air tothe kiln to maintain combustion therein, and means for automaticallyintermittently increasing the speed of the motor in response toincreasing temperature in the kiln and intermittently decreasing thespeed in response to de-. creasing temperature.

2. The combination of a rotary kiln for heating a' substance, a variablespeed motor for driving the kiln, means for conducting fuel and air tothe kiln to maintain combustiontherein, and means forintermittentlyincreasing the speed of the motor in response toincreasing temperature in the kiln and intermittently decreasing thespeed in response to decreasing temperature, said means including apilot motor for controlling the variable speed motor, a photoelectriccell trained. onto the substance in the kiln, relay means and a contactmaking and breaking device for controlling the pilot motor, and meansconnected be- 3. The combination of a rotary kiln for heating asubstance, a, variable speed motor for driving the kiln, means forconducting fuel and air to the kiln to maintain combustion therein, andmeans for automatically intermittently increasing the speed of the motorin response to increasing temperature in the kiln and intermittentlydecreasing the speed in response to decreasing temperature, said meansincluding a temperature responsive device associated with the kiln, anelecthetime delay relay and the contact making and breaking device.

AUBREY SMITH.

